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annulus

[an-yuh-luh s]
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noun, plural an·nu·li [an-yuh-lahy] /ˈæn yəˌlaɪ/, an·nu·lus·es.
  1. a ring; a ringlike part, band, or space.
  2. Geometry. the space between two concentric circles on a plane.
  3. the veil remnant on a mushroom stalk.
  4. a growth ring, as on the cross section of a tree trunk, that can be used to estimate age.
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Origin of annulus

1555–65; < Latin, variant of ānulus, equivalent to ān(us) ring + -ulus -ule
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for annulus

annulus

noun plural -li (-ˌlaɪ) or -luses
  1. the area between two concentric circles
  2. a ring-shaped part, figure, or space
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Word Origin

C16: from Latin, variant of ānulus ring
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for annulus

n.

1560s, medical, from misspelling of Latin anulus "little ring, finger ring," a diminutive of anus (see anus).

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Online Etymology Dictionary, © 2010 Douglas Harper

annulus in Medicine

annulus

n. pl. an•nu•lus•es
  1. A circular or ring-shaped structure.
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The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

annulus in Science

annulus

[ănyə-ləs]
Plural annuluses annuli (ănyə-lī′)
  1. A ringlike figure, part, structure, or marking, such as a growth ring on the scale of a fish.
  2. A ring or group of specialized cells around the sporangia of many ferns. By changing shape in response to variations in humidity, it breaks open the sporangium and then releases the spores with a whipping motion.
  3. The ringlike remains of a membrane (called a veil), found around the stipes of certain basidiomycete mushrooms. The presence or absence of an annulus is often used to identify the species of an individual mushroom.
  4. The figure bounded by and containing the area between two concentric circles.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.